How long does a female dog stay in heat?

Knowing how long a female dog stays in heat matters for safety, planning, and the dog’s welfare—so you can protect her from unwanted mating, choose the right time for spaying, manage intact males, and make reliable boarding or pet-sitting arrangements.

How understanding your female dog’s heat cycle benefits both of you

When a female dog enters her heat cycle, everyday routines change: walks and outings need more supervision because intact males may follow or try to escape to reach her, and socialization opportunities such as dog parks are often best avoided for the duration of the cycle. If you’re weighing spay timing, understanding typical cycle length helps you pick a safe point for surgery and recovery. For those considering breeding, knowing the window of fertility shapes responsible mating choices. And when arranging boarding or a pet-sitter, telling them the expected timeline and special handling needs keeps your dog safe and minimizes stress.

Heat duration: what to expect in most female dogs

On average a female dog’s entire heat cycle lasts roughly two to four weeks, though the fertile window is shorter and the full cycle stages extend beyond that.

The cycle is commonly divided into three main phases. Proestrus usually lasts about 7–10 days and is when you’ll most often see bloody discharge and swelling; she may attract males but generally is not receptive. Estrus follows and often lasts around 3–9 days—this is the period when ovulation is likely and a female may stand to be bred. Diestrus then begins after ovulation and is longer, representing the body’s return toward baseline and lasting several weeks. Between heats there is an anestrus phase; most dogs cycle every 6–12 months, with smaller breeds tending toward shorter gaps and large or giant breeds sometimes going longer. Individual dogs and breeds vary, so those averages may shift for your pet.

Hormones at work — the biology behind estrus in female dogs

The estrous cycle is driven by shifting hormones and is aimed at preparing the dog’s body for potential pregnancy. Rising estrogen levels produced by developing ovarian follicles are likely linked to the visible signs in proestrus—swelling, discharge, and behavioral changes—while a surge of luteinizing hormone (LH) triggers ovulation. After ovulation, progesterone from the corpus luteum becomes dominant and supports the uterus whether or not pregnancy occurs. The uterus and ovaries undergo predictable physiological changes during these phases, and the dog’s behaviors—more frequent urination, marking, tail “flagging,” or sudden friendliness or irritability—are commonly tied to those hormonal shifts.

When heats tend to start: age, breed and cycling patterns

When a female first comes into heat and how often cycles recur depends on a mix of internal and external factors. Age at first heat varies—many small and medium-breed dogs show their first cycle between six and twelve months, while larger breeds may not until 12–24 months. Breed and body size commonly influence both age at first heat and interval length; toy and small breeds often cycle more frequently than large breeds. Some breeds show seasonality tied to daylight length, though many household dogs will cycle without strict seasonal patterns. Nutrition, general health, body condition, and stress or illness can delay or alter cycles; for example, underweight dogs or those with endocrine issues may have irregular or absent heats.

Health risks and red flags: when to contact your veterinarian

Most heats are physiologic and uncomplicated, but some signs should prompt prompt veterinary evaluation. Prolonged or very heavy bleeding that soaks bedding or persists beyond typical duration may indicate a problem. A foul-smelling vaginal discharge, fever, persistent lethargy, or loss of appetite could suggest pyometra (a potentially life-threatening uterine infection) and requires immediate care. Sudden extremes in behavior, severe abdominal pain, refusal to eat or drink, or persistent swelling and abnormal lumps in the mammary chain or abdomen are also red flags. If you’re unsure whether a sign is concerning, it’s better to check with your veterinarian sooner rather than later.

Practical owner actions during a heat cycle — a week-by-week approach

At first signs—swollen vulva, bloody discharge, more frequent urination—begin by noting the calendar date and the nature of the discharge (color, amount, odor) so you have a clear timeline. Stage the cycle mentally: proestrus often involves bleeding and attraction of males, estrus is when she may accept males, and diestrus is the quieting phase. Immediately adjust containment and supervision: keep her on a short, secure leash outdoors, never leave her unattended in a yard without secure fencing, and avoid off-leash areas where intact males could access her. When contacting your veterinarian, report the start date, any changes in appetite or behavior, the appearance of discharge, and whether she has had contact with intact males. If you observe signs listed under medical red flags, call the clinic right away and be prepared to provide those same timeline details and a recent temperature if possible.

Managing the home and training while your dog is in heat

Practical home modifications reduce risk and stress. Ensure fencing is secure and evaluate potential escape routes; a double-gate or supervised transition area helps prevent quick escapes when entering or exiting. Keep her on leash and avoid dog parks or multi-dog daycare until the cycle ends. Short, frequent training sessions and mental enrichment—food puzzles, scent games, and calm obedience work—can redirect arousal and provide a predictable routine. Wash bedding frequently to remove scent cues that attract males, and where possible maintain separate sleeping areas so male dogs in the household are not continuously exposed. I typically advise owners to plan extra indoor enrichment during the first and second weeks, when behavior can be most changeable.

Helpful supplies and gear to get you through heat periods

A handful of items makes life cleaner and safer. Dog diapers or reusable heat pants can manage discharge and protect upholstery; note that diapers do not reliably prevent mating if a male gains access, so they are for hygiene rather than a barrier to breeding. Belly bands are useful for males in the household to prevent marking around a heat female. A sturdy leash and a well-fitted harness give better control during walks than a collar alone. Keep extra washable bedding, absorbent pads, enzymatic cleaners, and disposable gloves on hand for quick cleanup. For stress reduction, pheromone diffusers (such as dog-appeasing pheromone) or veterinarian-recommended calming supplements may help—always check with your vet before starting any supplement or medication, especially during heat.

Spay or breed? Key considerations before you decide

If you’re contemplating spaying, discussing timing with your veterinarian is important; many vets prefer waiting until recovery from the current cycle is complete and the dog is in good body condition. Spaying during an active estrus is possible but may carry slightly higher surgical risk depending on the individual; your vet will advise based on the dog’s state. For breeding, work with a reproductive veterinarian or an experienced breeder to time mating to the fertile window with appropriate health testing and clearances. Keep in mind responsible breeding involves health screening, honest risk assessment, and planning for neonatal care; if any part of that is uncertain, spaying is generally the safer option for most companion dogs.

Essentials to remember: a quick owner checklist

Record-keeping pays off: mark every heat’s start and end dates, note behaviors and any medical signs, and share that history with your veterinarian and any caregiver. Treat heat as a temporary but important change in your dog’s routine—manage access, avoid exposure to intact males, maintain hygiene, and consult your veterinarian if anything deviates from expected patterns. With attentive management most dogs move through heat safely and return to normal behavior within weeks, and you’ll be better prepared if an issue arises.

Trusted references and further reading

• Merck Veterinary Manual: “Canine Estrous Cycle” — Merck Veterinary Manual, Merck & Co., Inc.
• American Veterinary Medical Association (AVMA): “Spaying and Neutering” and related client education on reproductive cycles
• Concannon PW. “Reproductive cycles of the domestic dog.” Veterinary Clinics of North America: Small Animal Practice (review article on canine reproduction)
• Johnston SD, Kustritz MV, Olson P. Canine and Feline Theriogenology (textbook covering clinical reproductive management)
• American College of Theriogenologists: client resources on breeding and reproductive health
• Clinical guidance and patient handouts from the American Animal Hospital Association (AAHA) on spay/neuter and reproductive care